A Caterpillar in the Carina Nebula. Scattered across the enormous Carina nebula are numerous dense clumps of cosmic gas and dust called Bok globules, including this one, which resembles a huge glowing caterpillar. First described by by astronomer Bart Bok, the globules are relatively small, dark, and cold regions made up of molecular hydrogen, carbon oxides, helium, and dust. The glowing edge of the caterpillar indicates that it is being photoionized by the hottest stars in the surrounding cluster. It has been hypothesized that stars may form inside these dusty cocoons.